(a) Field of the Invention The present invention relates to a polymer blend composition comprising a dielectric elastomer, an actuator film manufactured using the same, and an actuator comprising the film.
(b) Description of the Related Art
A piezoelectric element is an element showing a piezoelectric effect which converts electrical energy into mechanical energy, and piezoelectric ceramic materials such as quartz, tourmaline, Rochelle salt or the like have been usually used. However, the ceramic materials are highly brittle and hard to process, and thus their application is limited.
Recently, there are growing concerns about dielectric elastomers that exhibit the piezoelectric effect and are also easy to process. The dielectric elastomers have recently gained interest as a material to overcome the drawbacks of the ceramic materials, because they have a high power/weight ratio and high energy efficiency, and are very flexible and easy to process. Unlike hydraulic or aerodynamic actuators, dielectric elastomer actuators do not need life-limited components such as gears and bearings, and this allows a precise design.
The dielectric elastomer actuators have advantages of very rapidly converting electrical energy into mechanical energy and having high displacement values. However, they have a disadvantage of requiring high operating voltage, and many studies on this problem are still under progress. The dielectric elastomer actuators are known to be driven by the Maxwell stress σ (σ=∈0∈E2: wherein ∈0, ∈ and E represent the vacuum permittivity, the dielectric constant, and the electric field strength, respectively).
That is, the Maxwell stress is proportional to the dielectric constant. Thus, there have been attempts to improve operating properties of the actuators by adding conductive fillers such as ceramic filler or carbon black, graphite, and metal particles to dielectric elastomers such as thermoplastic elastomers so as to increase the dielectric constant of the composites. However, the addition of fillers greatly increases a dispersed phase of the fillers to a micrometer level, and a conductive pass is formed by filler aggregation to generate dielectric loss. Thus, there is a limit in the improvement of electromechanical conversion efficiency. In short, the addition of fillers is disadvantageous in that dielectric loss and leakage current are increased, and breakdown strength properties are deteriorated.
To solve these problems, recent studies have suggested a method of directly grafting copper (Cu) phthalocyanine having high dielectric constant or aniline oligomer having excellent electrical conductivity with a urethane-based elastomer or a polyvinylidene fluoride-based polymer. However, the reactivity of this chemical grafting method can be highly restricted depending on the type of dielectric elastomer or the composition to be grafted, and the increase in dielectric loss and the deterioration of breakdown strength properties are also inevitable.